1. Field of the Invention
The present invention relates to a linear guide rail and a method for working the same and, in particular, to an improvement in working of one or more raceway grooves of such linear guide rail.
2. Description of the Related Art
Conventionally, a manufacture of a linear guide rail is carried out through, for example, a step shown in FIGS. 15A to 15F. That is, steel material (work) used as a linear guide rail blank work is drawn to thereby form the outer shape of the linear guide rail as well as the shape of each of raceway grooves 2 (see FIG. 15A).
Next, the groove bottom portion of the raceway groove 2 of the thus drawn-worked linear guide rail work is cut to thereby form a wire holder groove 3(or, in some cases, an oil storage groove) for insertion of a wire holder and/or a base surface display line (or a base surface display groove) 4 for displaying a mounting base surface Wbs (see FIG. 15B).
The above operations are executed as pre-working operations.
After then, the linear guide rail work is heat treated.
Next, the linear guide rail is bored to thereby make a mounting bolt hole 5 (see FIG. 15C).
Then, the upper surface Wa and lower surface Wc of the guide rail work are finish ground (see FIG. 15D).
Further, the raceway grooves 2 as well as the two side surfaces Wbs and Wb of the guide rail work are finish ground (see FIG. 15E). The groove grinding operation, as shown in FIG. 15F, is carried out by the simultaneous grinding operation of the two side surfaces of the guide rail work.
However, the above-mentioned pre-working operations, that is, the drawing and cutting operations provides working accuracy and surface roughness which are not sufficient as finish accuracy and, therefore, as a finishing step, there is necessary a grinding operation even in the case of a product which does not require high accuracy, which raises a problem that it takes long time to work the guide rail and thus the working cost of the guide rail becomes expensive.
That is, in the above drawing operation, there can be provided only the insufficient working accuracy and thus, in the grinding operation, it is necessary to provide rather large grinding allowance, which results in the longer grinding time.
On the other hand, in order to work a guide rail as accurately as possible in the drawing operation, the number of times of drawing must be increased. In fact, however, each time the guide rail work is drawn, it is necessary to execute the following pre- and post-treatments: that is, (1) leader formation (a treatment to narrow the leading portion of the guide rail work so as to be insertable into a die); (2) annealing; (3) shot peening for removing scales developed in a heat treatment; and, (4) a phosphate film treatment. This raises a problem that the working cost of the guide rail is expensive and the working accuracy thereof is not so good.
The present invention aims at eliminating the drawbacks found in the above-mentioned conventional linear guide rail and the conventional method for working the same. Accordingly, it is an object of the invention to provide a linear guide rail and a method for working the same which, by applying a rolling technique to a linear groove to be formed in the linear guide rail, can reduce the working time and cost of the linear guide rail as well as can secure the necessary working accuracy of the guide rail.
In attaining the above object, according to a first aspect of the invention, there is provided a linear guide rail including one or more raceway grooves along which rolling bodies roll, wherein the raceway grooves are respectively rolled.
According to a second aspect of the invention, in a linear guide rail according to the first aspect of the invention, the surface roughness of each of the raceway grooves in the longitudinal direction thereof is in the range of 0.05-0.2 Ra.
According to a third aspect of the invention, in a linear guide rail according to the first aspect of the invention, the lower surface of the linear guide rail is formed in such a dented shape that the width-direction two end portions thereof are slightly raised over the width-direction central portion thereof.
According to a fourth aspect of the invention, in a linear guide rail according to the first aspect of the invention, a decarburized layer of the surface of a rail blank work is removed before the rail blank work is rolled.
And, according to a fifth aspect of the invention, there is provided a method for working a linear guide rail having one or more raceway grooves along which rolling bodies can roll, wherein, using two or more rotary dies each including a projection-shaped working portion matched in shape to the raceway groove, the raceway grooves are rolled on a rail blank work.
According to a sixth aspect of the invention, in a method according to the fifth aspect to the invention, wherein at the same time when the raceway grooves are rolled on a rail blank work, the lower surface of the rail blank work is ground or cut, using two or more rotary dies each including a projection-shaped working portion matched in shape to the raceway groove.
According to a seventh aspect of the invention, in a method according to the fifth aspect of the invention, as the need arises, at least one of chamfering of the corner portions of the linear guide rail, formation of an oil storage groove in the bottom portion of each of the raceway grooves, and formation of a base surface display line is carried out using the rotary dies simultaneously when the raceway grooves of the linear guide rail are rolled using the same rotary dies.
According to an eighth aspect of the invention, in a method according to the fifth aspect of the invention, by rolling the raceway grooves using rotary dies, the width-direction two end portions of a mounting surface of the linear guide rail are projected slightly up from the width-direction central portion thereof.
According to a ninth aspect of the invention, in a method according to the fifth aspect of the invention, there is further included a sensor for measuring a distance between the working positions of the rotary dies or a distance between the positions of the portions adjacent to the working positions, and, while controlling a distance between the rotary dies so as to be constant, a distance between the raceway grooves can be maintained stably.
According to a tenth aspect of the invention, in a method according to the fifth aspect of the invention, there is further included a sensor for measuring the positions of the raceway grooves just after the raceway grooves are rolled by the rotary dies, and, the positions of the raceway grooves are detected by the sensor and, in accordance with the thus detected values, the positions of the rotary dies are controlled to thereby maintain the inter-raceway groove distance (the distance between the raceway grooves) stably.
According to an eleventh aspect of the invention, in a method according to the fifth aspect of the invention, there are included two rotary dies disposed spaced from each other on the side of two raceway grooves to be formed on one side of the linear guide rail and a rotary die disposed on the other side of the linear guide rail so as to be asymmetric with respect to the above two rotary dies, whereby the linear guide rail is bent formed using the above rotary dies simultaneously when the raceway grooves are rolled using the same rotary dies, thereby being able to produce a linear guide rail having a curvature.
According to a twelfth aspect of the invention, in a method according to the fifth aspect of the invention, the raceway grooves of the linear guide rail are previously rolled using the rotary dies and are then heat treated and, after then, the raceway grooves are ground to thereby finish the same with high accuracy.
As has been described hereinbefore, according to the invention, the raceway grooves of a linear guide rail are rolled in a single step by using rotary dies each having a projection-shaped working portion matched in shape to the raceway groove and, therefore, there is required a smaller working force than a force which is required in the above-mentioned conventional drawing operation. Also, the rotary dies wear less and thus the lives of the dies can be extended. The tissues of the rolling surface are continuous and are thus high in strength. Further, in the case of a product (a linear guide rail) which does not require high accuracy, the raceway grooves of such product can be worked with proper accuracy without cutting or grinding the raceway grooves after the linear guide rail blank work is drawn as in the conventional working method, which can shorten the working time as well as the working cost of the product (linear guide rail). Use of the rotary dies makes it easy to guide lubricant onto the working surface of the rail blank work.
Also, in case where chamfering of the corner portions of the present linear guide rail, formation of an oil storage groove in the bottom portion of each raceway groove, and formation of a base surface display line are carried out simultaneously using the same rotary dies, the working efficiency can be enhanced greatly.
By rolling the raceway grooves using the rotary dies, the width-direction two end portions of the mounting surface of the linear guide rail can be projected slightly up from the width-direction central portion thereof, which makes it possible to stabilize the mounting state of the linear guide rail more. That is, when a mounting bolt is tightened, the mounting contact surface of the rail spreads in the width direction thereof and, therefore, even when a lateral load is applied to the linear guide rail, the linear guide rail can stand firm, thereby being able to enhance the mounting strength of the linear guide rail.
Also, in case where the distance between the working positions of the rotary dies is measured and the measured value is fed back to thereby automatically control the inter-die distance so as to be constant, the distance between the raceway grooves of the product can be maintained more stably, which makes it possible to provide a linear guide rail of high quality.
And, in case where the rotary dies on the two sides of the linear guide rail are arranged asymmetric with respect to each other, the linear guide rail can be bent worked by these rotary dies simultaneously when the raceway grooves are rolled using the same rotary dies, thereby being able to provide a linear guide rail having a curvature.
Further, according to the invention, the raceway grooves of a linear guide rail are formed with high accuracy by cold rolling them and, therefore, even in case where, as the need arises, the raceway grooves are heat treated after such cold rolling and, after then, they are further ground in order to obtain higher accuracy, the grinding allowance of the raceway grooves can be minimized. Accordingly, when compared with the conventional working method, the grinding time of the raceway grooves can be shortened to thereby reduce the working cost of the linear guide rail as well as the degree of bending to be developed by the groove grinding operation can be reduced, so that the raceway grooves can be finished with high efficiency as well as with high accuracy.